Playing it by the book

Susannah Harker is deep in conversation with her French director Marianne Badrichani when I arrive. As Badrichani gets up, Harker implores her not to go. 'I may not know what to say,' she says, semi-despairingly, before conceding defeat. 'But you'll be nice to me,' she says, turning to me. 'Won't you?'

It's rather unexpected that an actress with such on-screen poise as Susannah Harker should come across as a little insecure in person. It's only an initial thing: soon, she is warm, enthusiastic and just a little luvvy-ish, complimenting me on my necklace, overjoyed I've read the script for her new play, eager to talk.

It transpires that today is the first day of rehearsal for The Little Black Book, an unusual two-hander by the French playwright Jean-Claude Carriere, in which she stars with Paul McGann. They haven't even done a read-through yet - some actors hate talking about a project before they feel fully acquainted with it. Maybe it's a spot of first-day-at-school nerves.

Never an actress to appear in public in a backless frock, as she puts it, Harker nonetheless seems to have been away from the spotlight for some time. She made her name in TV; first as the reporter Mattie Storin in House Of Cards and then as the pious Jane Bennett in Andrew Davies's adaptation of Pride And Prejudice. The two roles were sufficiently big and different to establish her profile as a household actress without pigeonholing her.

Harker had never wanted to be a TV actress anyway: 'Both my parents are actors; at drama school, I believed Shakespeare was my thing. Then the call from TV came, and, well, you know...' she trails off.

Recently, though, she has returned to the theatre - 'my home' as she calls it. She was on tour with Corin Redgrave in another play, The Browning Version, due in the West End later this year, when her agent put her up for The Little Black Book.

A hit in Europe, it has never been performed in the UK. Harker plays Suzanne, an enigmatic stranger who wanders into Jean-Jacques's flat and - intrigued by the book he keeps with the names of the women he has slept with - refuses to leave. Their relationship becomes a cat-and-mouse exploration into the meaning of love.

It's an ideal play for Harker who, for all her bubbly theatricality, has something inscrutable about her and admits to being fascinated by psychology. 'As I get older, I've become more interested in human behaviour and motivation,' she says. 'I'm convinced acting is 80 per cent psychology and 20 per cent technique, and perhaps a bit of talent.' 'As I get older' are words Harker uses a lot. As is 'inspiration'. 'I only do work that inspires me, work I connect with,' she says. 'Having a child [she has a son, Finlay, with the actor Iain Glen; the couple have since separated] certainly helps you focus on what you want to do. You have to be able to smell a part to want to do it.'

Increasingly, these 'inspirations' have been in the theatre rather than TV. 'TV has shifted radically in the last few years, thanks to the rise of reality TV and celebrity culture,' she says. 'More and more actors are moving into theatre in search of stimulation, whereas a decade ago it was the other way round. Although don't print that,' she laughs. 'I'll never work in TV again.'

She is quick to draw a line between her private life and her professional one, perhaps because her split from Glen was quite public: he had appeared with Nicole Kidman in The Blue Room and there were rumours that the friendship had had an impact on the marriage. 'I hide myself behind my job - that's partly why I do it,' she says. 'There should always be a line between oneself as an actor and as a person.'